1. Field of the Invention
The invention relates to an encoding device, a lamp, and a controlled lighting system, more particularly to an encoding device for a light-emitting-diode (LED) lamp, a lamp, and a controlled lighting system.
2. Description of the Related Art
Referring to FIG. 1, in a conventional method for controlling illumination of LED lamps 61, two twisted-pair lines are connected to two input ports of a LED lamp 61 for supplying power and control signals thereto. However, when a lighting system includes a large number of the LED lamps 61, a network system 62 formed by the twisted-pair lines becomes more complex, thereby making installation more difficult.
Referring to FIG. 2, U.S. Pat. No. 6,292,901 discloses a conventional control system that adopts a power/data protocol. The control system combines power and control signals such that each LED lamp 8 only requires one input port. As a result, a single transmission line is sufficient to control a light-emitting operation of a LED 82, thereby effectively reducing wiring complexity.
The conventional control system is adapted to control color emitted by a LED 82 in a lamp 8, and is coupled electrically to an adapter 63 that converts an alternating current (AC) power input into a direct current (DC) power output. The conventional control system includes an encoding device 71, and a decoding device 81 built into the lamp 8. Referring to FIGS. 3 and 5, the encoding device 71 includes a RS-485 receiver 711, a voltage regulator 712, and a pulse width modulation driver 713. The RS-485 receiver 711 converts a differential pair that contains a control signal into a digital signal. The voltage regulator 712 regulates the DC power output and provides regulated DC power to the pulse width modulation driver 713 for operation of the latter. The pulse width modulation driver 713 combines the digital signal and the regulated DC power, and outputs an AC square wave signal.
Referring to FIGS. 4 and 5, the decoding device 81 includes a voltage divider 811, receives the AC square wave signal through the transmission line, and converts the AC square wave signal into a voltage-divided signal in a digital format suitable for processing by a processor that enables the LED 82 to emit a specified color.
Referring to FIG. 6, U.S. Pat. No. 6,069,457 discloses a conventional control system that controls brightness of a gas discharge light bulb 94 in a lamp through a single transmission line, and that is coupled to an AC power source 93. The conventional control system includes a dimmer switch 91, and a decoder 92 built into the lamp. The dimmer switch 91 includes a pair of switches (SW1), (SW2) which are controlled by a user for causing the dimmer switch 91 to provide an output signal from an AC power signal of the AC power source 93. FIG. 7 shows four possible waveforms of the output signal, which correspond respectively to maintain brightness of the gas discharge light bulb 94, increase brightness of the gas discharge light bulb 94, reduce brightness of the gas discharge light bulb 94, and turn-off the gas discharge light bulb 94.
The decoder 92 receives the output signal through the transmission line, and controls brightness of the gas discharge light bulb 94 according to the waveform of the output signal. The decoder 92 is not configured to control the color of the light emitted by the gas discharge light bulb 94.